Harvesting mechanisms are used for grain harvesting with self-propelled combines. They usually have a horizontally orientated cutter bar for cutting crop stalks and a transverse conveying auger that feeds the cut crop to the feederhouse of the combine. A pickup reel is located above and in front of the cutter bar to gather the crop to be harvested and to direct crop to the cutter bar and the transverse conveying auger. The pickup reel rotates around a longitudinal axis and is provided with horizontal tine carriers distributed around the longitudinal axis. The tine carriers carry tines that engage the crop stalks.
The reel is usually rotatably mounted on reel supports that are provided on reel carrier arms. The carrier arms are pivotably mounted behind the cutter bar on the frame of the harvesting mechanism and pivot around a horizontal axis transverse to the direction of forward movement. The angle of the reel carrier arm is adjusted by a hydraulic cylinder around the axis, and thus adjusts the height of the reel relative to ground level and the cutter bar. An additional hydraulic cylinder shifts the reel along the reel carrier arm. The position of the reel can thus be varied in the forward and backward direction.
The reel carrier arms are usually straight over their entire length, as shown in the prior art in GB 1 501 639 A, GB 1 574 033 A and WO 03/049532 A. Alternatively, reel carrier arms are provided with bends or angles. Usually the part of the reel carrier arm that cooperates with the reel support is straight, as shown in U.S. Pat. No. 4,800,711, U.S. Pat. No. 6,029,429, DE 195 08 887 C, and DE 195 29 067 A. Therefore, when the reel is shifted along the reel carrier arm, the reel moves in a straight line. The angle or slope of the reel carrier arm relative to the horizontal depends on the pivoting angle of the reel carrier arm around the horizontal axis.
Additionally, some harvesting mechanisms have a two part intake mechanism. A front bottom part carries the cutter bar and is movable in the forward direction. A rear bottom part is fixed solidly to the harvesting mechanism frame. In order to adapt the harvesting mechanism to a crop such as rapeseed, for example, the front bottom part is moved forward. Problems can arise in adjustment of the reel position because collisions between the reel and cutter bar are possible when the front bottom part is adjusted forward. Specifically collisions happen in the area of the cutter bar if the reel is adjusted forward or is lowered too far.
Thus, precautions are taken to prevent such collisions. In U.S. Pat. No. 4,800,711 a mechanical coupling is provided between the cutter bar and the reel carrier arm by a lever mechanism that automatically moves the reel carrier arm vertically as a function of the horizontal position of the cutter bar. A similar mechanical coupling between the reel carrier arm and cutter bar which has a radial cam and a guide roller is described in WO 03/049532 A. To prevent collisions of the reel with the cutter bar, DE 195 08 887 C provides an electronic coupling for positioning the cutting bar via a connection to a sensor that controls an actuator.
The known coupling between the position of the cutting bar and the vertical reel position is disadvantageous in that the operator cannot switch to certain reel positions in a manner that is easily known to him because certain reel positions are blocked mechanically or electronically. Furthermore, the above mechanical and electronic components are relatively expensive and are susceptible to fouling and damage.
Potential collisions between the reel and cutter bar also arises in other types of harvesting mechanisms, especially those with conveyor belts that transport the crop back to a transverse conveying auger which then feeds the crop to the feederhouse of a combine, as described in GB 1 501 639 A, GB 1 574 033 A and GB 1 602 067 A. A sufficiently long horizontal adjustment path of the reel is required to be able to move the reel far enough forward to receive laid crop, and also to be able to move the reel far enough backward for rapeseed harvest to press the crop mat under the transverse conveying auger. The reel should operate below the cutting bar in the forward position but not lie on the conveyor belt in the rear position. This problem could be resolved by a mechanical arrangement, similar to the previously described couplings between the position of the cutter bar and the vertical adjustable reel position, which automatically raises the reel arm when it is moved backward. However, this configuration also has the above-described shortcomings.